The population of opioid dependent pregnant women and their fetuses and infants are a highly vulnerable and complex group that are currently poorly understood. Infants display a range of physiologic and behavioral problems that are widely variable, have unknown pathophysiology, and are characterized by significant deficits in neuroregulatory functioning. Research by this team has shown that methadone negatively affects fetal neurobehaviors in late gestation, and that severity of newborn neuroregulatory dysfunction is related to maternal and infant autonomic nervous system activity. New research has shown the optimality of buprenorphine maintenance during pregnancy as compared to methadone, principally due to improved neonatal outcomes, which is likely to result in increased numbers of providers and patients seeking this medication for treatment of opioid dependency during pregnancy. However, little information regarding the effects of buprenorphine on the developing fetus and infant exists. Pilot data from this group of investigators has suggested that buprenorphine, as compared to methadone-exposed fetuses, exhibit more optimal fetal functioning in the second and third trimesters of gestation. With this proposed research project, we intend to track the longitudinal neurobehavioral development of the buprenorphine-exposed fetus across gestation through 1 month of age in an effort to determine the safety of this medication for use during gestation, the relationship between maternal physiologic changes due to buprenorphine administration and newborn functioning, and to determine potential fetal neurobehavioral markers that may predict NAS expression and infant neurobehavioral outcome. Comparisons to results from a similar project in methadone-exposed pregnancies will be made. This proposal seeks to advance the way we inform the treatment of the opioid dependent woman during pregnancy and her infant after birth.